The invention relates to a new process for the preparation of indoline derivatives, which are intermediates for the preparation of 1,2,3,4,10,10a-hexahydropyrazino-[1,2:a]indoles.
1,2,3,4,10,10A-Hexahydropyrazino[1,2:a]indoles are described in U.S. Pat. No. 3,853,878 and German Offenleg. 21 62 422 and 22 50 493. These compounds have valuable pharmacological properties and can be used as medicaments, particularly for the treatment of hypertension.
Known methods for preparing these substances are unsatisfactory since they require reduction with complex metal hydrides or diborane. Thus, known preparative methods are expensive and dangerous to carry out on an industrial scale. Although these hexahydropyrazinoindoles can be made from the corresponding 2-halomethyindolines, no industrially acceptable method of preparation is known for these intermediates.